1. Field of the Invention
The present invention relates generally to devices capable of sensing motion and speed. More specifically, it relates to estimating shifting and rotational speeds of devices using imaging and other types of sensors.
2. Description of the Related Art
Presently, motion sensors, such as accelerometers and gyroscopes are not suitable for estimating the speed of complex motions of devices in which they are contained or to which they are attached. This is because they do not efficiently track constant movements. Their mechanisms generally depend on inertial sensors which require integrating acceleration over time to compute speed resulting in potential drifting errors. This is true, for example, with accelerometers and gyroscopes. Another method to measure motion of devices is using an imager which measures the overall “optical flow,” which refers to the pattern of apparent motion of objects, surfaces, and edges in a visual scene caused by the relative motion between an observer (an eye or a camera) and the scene. Measuring the overall optical flow in two dimensions (e.g., left-right and up-down) is computationally feasible, but this method fails to distinguish between the linear shifting and rotation movement of the device. Measuring optical flow in more than two dimensions (e.g., 3 to 6), requires substantially more processing power, because the analysis of complex optical flow patterns is required.
Therefore, existing solutions for motion speed estimation of a device limit the design of natural user interfaces for digital content where sensing a user's gesture or body part motion may be important. Furthermore, combining various types of sensors to achieve accurate motion speed estimation requires high computational power and increases the computational complexity of relevant algorithms. It would be useful to have devices that can measure their own egomotion speeds without having to install additional hardware components.